1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a sheet by conveying the sheet, and more particularly, to an image forming apparatus in which, when a sheet in an abnormal state is discharged, the user can discriminate that sheet from normal sheets.
2. Description of the Related Art
In conventional image forming apparatuses, an image is formed on a sheet, and then the sheet is discharged. Such an image forming apparatus detects, when a sheet being conveyed is jammed in an abnormal state, i.e., when a so-called jam is occurs, the jam using a jam detection sensor, and immediately stops the operation.
However, a sheet that is not jammed even in an abnormal state is discharged without any notification. For example, such a sheet has the problem that an image is obliquely formed on the sheet due to skew of the sheet, a corner of the sheet is folded, or a plurality of sheets are superposed.
Since such a sheet is discharged and mounted as a normal sheet even in an abnormal state, the user does not notice the problem. Even if the user knows that such a sheet is in an abnormal state, the user's action differs depending on the type of abnormality. That is, when a plurality of sheets are conveyed in a superposed state, it is only necessary for the user to extract blank sheets from the bundle of discharged sheets. On the other hand, when the sheet skews or a corner of the sheet is folded, it is necessary for the user to extract the sheet from the bundle of discharged sheets, and insert a normal sheet having an image formed thereon into the extracted position.